Staff: Mentor

You should be able to find this in any number of physics books. In any case, the basic idea is this:

An object in circular motion has at any point a tangential speed V= (omega)r. To find the acceleration, take two points separated by d(theta). Draw the vectors representing these two velocities. The difference between them (which points towards the center) is dV = Vd(theta). The acceleration a = dV/dt = Vd(theta)/dt = V(omega)= V(V/r) = V2/r.